Generally, the methods for preparing nanoporous materials of an inorganic compound such as silica using an organic compound as a template are widely used in order to synthesize nanoporous materials using a template. Particularly, since the method for synthesizing nanoporous silica using a surfactant capable of forming micells as a template, among organic compounds, was discovered, there have been many reports in connection with application to chemistry, biochemistry, optical science and electrical industry. Such inorganic compounds possess useful properties applied to molecule sensors, agents for compound separation, chromatography agents, adsorbing agents, catalysts and functional devices such as light emitting devices and thus, are researched by many laboratories. Specifically, the sol-gel template method (SGTM) is most commonly used to synthesize a wide range of nano-sized inorganic compounds having various structures, which are synthesized by ionic bond or hydrogen bond between proper cationic parts of assembled organic molecules and adsorbing inorganic compound.
Many research groups in the world are synthesizing nano-sized structures with various sizes and structures by using such surfactants. Particularly, 2-amino-N-dodecylacetamide which is one of the glycine-derived surfactant having the peptide structure is applied in the medical field. The surfactants of this type are commonly synthesized by attaching an amine protector such as butyloxycarbonyl (BOC) and fluorenylmethyloxycarbonyl (Fmoc) to an end of an amine to lower the reactivity. Thus, the synthesis is simple, but the used agents such as BOC and Fmoc are rather expensive. On the other hand, the synthesis method using phthalic anhydride is advantageously cheap and can realize mass production of surfactants. However, this method needs a large amount of aromatic compounds, synthesizing apparatus is complex and a large amount of energy is consumed.
Thus, for the synthesis of 2-amino-N-dodecylacetamide which is one of the glycine-derived surfactant synthesized by the conventional method, the peptide synthesizing agent may be used in those fields including the value-added medicinal fields, where the agent is used in a tiny amount, but is not suitable for a template to synthesize commercially applicable nanostructures where it is used in a large amount. Accordingly, in order to solve such problems, researches have been diversely attempted to develop new synthesis.
As a method for synthesizing nanostructures using a surfactant, Kresge et al. have synthesized nanosilica structures (MCM-41) using alkylammonium bromide (See, Kresge C T, Leonowicz M E, Roth W J, Vartuli J, Beck J S, Nature, 359, 710, 1992). By this method, it was possible to produce hexagonal nanostructures having a pore size of 2 to 3 nm. However, these structures had problems that they should be synthesized by the hydrothermal method under strong basic conditions and were easily collapsed in an aqueous solution.
Pinnavaia et al. have synthesized silica nanostructures (HMS) using an alkylamine(CnH2n+1NH2) which was electrically neutral (Peter T. Taney and Thomas J. Pinnavaia, Science, 1995, 267, 865-867). This method could produce nanostructures with cumulated pores, which had a pore size of 2 to 3 nm, at room temperature. However, these structures were physically weak and showed poor alignment. The same research group synthesized very stable elliptical mesoporous structures (MSU-G) using a surfactant (CnH2n+1NH(CH2)2NH2) which had an electrically neutral secondary amine group (S. S. Kim, T. J. Pinnavaia, Science, 1998, 282:1302-1305). Owing to the amine group with the double bond, the elliptical structures were self-assembled. Also, through the self-assembly, strong hydrogen bonds were formed, and the self-assembled structures were not broken down even at the high temperature in the hydrothermal synthesis (for 100 to 150 hours), whereby thermal stability similar to zeolite was secured. As compared to the existing mesoporous materials, these structures showed a high Q4 (the whole single bond of Si being bonded)/Q3. Further, this group reported that the structures which were synthesized using the electrically neutral amine group showed higher thermal stability than a surfactant having ionic properties. However, these structures were found to have problems in alignment and energy consumption caused by heating at a thigh temperature.
Also, Che et al. have synthesized N-acyl-L-alanine which is an amino acid surfactant and synthesized helical mesoporous structures using the amino acid surfactant as a template and an amino silane copolymer as a co-structured directing agent (CSDA), in which the mesoporous structure has a pore size of about 2.2 nm (S. Che, Z. Liu, T. Ohsuna, K. Sakamoto, O. Terasaki and T. Tatsumi Nature 429, 281-284). However, this synthesis had problems in that the synthesis cannot be reproduced since it used copolymers which made the method complicated, the pore size was small and safety was not secured.
As described above, various methods for synthesizing silica nanostructures using a surfactant have been disclosed and the present inventors also have synthesized one-dimensional silica helical mesoporous structures by using a glycine-derived surfactant and adjusting the temperature of the gelling synthesis. Thus, the method has been completed.